| Food Composition Data: A User's Perspective (1987) |
|The uses of food composition data|
|NCI food data needs: impact on coding systems|
United States studies
Uses of food composition data
Implications for infoods
RITVA R. BUTRUM
National Cancer Institute, Washington, D.C., USA
The National Cancer Institute (NCI) supports many different types of research on the relationship between nutrition and cancer, including studies in prevention, epidemiology, etiology, basic cellular mechanisms, treatment, and information dissemination. As a result of conducting this research, major deficiencies in existing food data bases have become apparent. Problems range from the unavailability of food data to questionable data validity, reliability, accessibility, and interpretation.
Food data problems are especially evident in epidemiologic studies, which focus on populations' dietary differences and their relationships to cancer incidence. International variations in diet can be distinguished by broad nutrient-food categories, but detailed information is lacking on the nutrient content of many foodstuffs consumed by different peoples and their subgroups. In addition, comprehensive data are unavailable for the non-nutrient chemical components of food, which represent protection for, or risks to, good health.
Thus, creating a comprehensive food composition data network as proposed by INFOODS, covering the spectrum of biologic activity from nutrients to contaminants, would greatly aid cancer epidemiologists, researchers, clinicians, educators, and public policy-makers. The purpose of this paper is to highlight selected NCI-supported projects which would benefit from the development of such a system. Table 1 presents users of food composition data at the international, national, local, and individual levels. The objectives of each of these researchers' projects is then discussed with their needs relative to the development of an internationally acceptable coding system.
At the international level, NCI is supporting a variety of diet, nutrition, and cancer studies involving food composition data. The first study, now in progress in Puerto Rico, is examining the exposures of staple foods to high levels of toxic substances such as pesticides and chemical fertilizers. Many Puerto Ricans derive a major source of their caloric intake from maize, which may be the principal vehicle for exposing the population to potential carcinogens.
Table 1. NCI-supported research projects
|Principal investigator||Project title||Location||Objective||Rationale|
|Angel A. Roman-Franco||Cancer Control Research Grant for Puerto Ricoa||San Juan, Puerto Rico||Obtain information relating to the degree of exposure of staple foods to high levels of toxic substances, e.g. pesticides and chemical fertilizers||The bulk of calories comes from a single staple, which may be the principal vehicle for exposing the population to potential carcinogens|
|T. Colin Cambell||Dietary Selenium and Cancera||People's Republic of China||Evaluate the role of dietary selenium as a risk factor for various cancers||In vitro and in vivo studies have demonstrated that Se supplements reduce the incidence of carcinogen-induced and spontaneous neoplasms|
|Li Ping||Nutrition Intervention Triala||Linxian, China||Conduct intervention trials using micro-nutrients administered to oesophageal dysplasia patients and to a general population at high risk||Segments of the population are known to have poor intakes of multiple micro-nutrients, which may correlate with cancer risk|
|Ruth M. Hicks||Carcinogenesis in Human and Rat Bladder Tissuesa||London, UK||Compare the effects of promoters (e.g. saccharin and tryptophan) and anti-promoters (e.g. retinoids) on previously initiated human and rat bladder organ cultures||This study will determine if the rat is an appropriate model for screening human bladder carcinogens|
|Olli P. Heinonen||US-Finland Studies of Nutrition and Cancera||Helsinki, Finland||Determine whether beta-carotene or vitamin E supplementation is effective in preventing lung cancer in heavy smokers||Dietary beta-carotene has been inversely correlated with lung cancer incidence in epidemiologic studies|
|Khursheed N. Jeejeebhoy||Nutritional Assessment of Cancer Patientsa||Toronto, Canada||Assess the efficacy of three levels of nutritional support in maintaining lean body mass of patients with lung or colorectal cancer||This study will provide insight into the nutritional aspects of patients with advancing malignancy|
|Abraham M. Nomura||Cancer Epidemiology of the Migrant Japanese in Hawaii(b)||Honolulu, Hawaii||Distinguish the relationships between dietary habits and incidence of cancers in a migrant population||Culture and environmental conditions have been found to influence cancer risk|
|Ritva Butrum||Low Fat Diet in Women with Stage II Breast Cancerb||Boston, Mass.; Atlanta, Gal; Los Angeles, Calif.; Iowa City, Iowa; Chicago, 111.; Houston, Tex.; New York, N.Y.; Pittsburgh, Pa.||Identify the effect of a low-fat diet on disease relapse and overall survival in stage II breast-cancer patients||Epidemiologic and case-control studies have linked a high-fat diet to increased incidence and mortality from breast cancer|
|Low Fat Diet in Women at Increased Risk for Breast Cancerb||Houston, Tex.; Seattle, Wash.; Cincinnati, Ohio||Evaluate whether manipulation of dietary fat will slow or halt the "promotion" phase of carcinogenesis||Reduction of dietary fat, even if done late in the promotion phase, has resulted in a reduction of breast-cancer incidence in animal models|
|P. J. Van Soest, J. A. Marlett||Methodology and Analysis of Fiber Components in Foodb||Ithaca, N.Y.; Madison, Wis.||Develop methods for fibre analysis and analyse total fibre and individual dietary fibre components in US foods||A reliable data base of total dietary fibre and fibre fractions is needed for NCI studies|
|Phyllis E. Brown||Adenomatous Colonic Polyps, A Vitamers and MFO Inductionb||Chicago, III.||Assess the efficacy of using beta carotene to inhibit colonic polyps and/or colonic cancer||Epidemiologic and laboratory research have demonstrated the preventive effects of carotenoids|
|A. R. Patel||Dietary Markers for Epidemiologic Studies of Cancerb||To be determined||Identify markers of past or present dietary exposure||Markers will be useful in validating or conducting nutritionally focused studies in cancer epidemiology|
|C. Butterworth, R. Riviln||Clinical Nutrition Research Units (CNRUs)||Birmingham, Ala.; New York, N.Y.||Stimulate multi-disciplinary research, education, and training in nutrition||Co-ordinated effort, intellectual stimulation, and use of shared resources can funkier our knowledge of nutrition and cancer|
|Paul Van Nevel||Cancer Prevention Awareness Program: Nutrition and Cancerb||Bethesda, Md.||Stimulate public awareness of the relationship between specific dietary patterns and cancer risk||Epidemiologic and laboratory evidence provides support for interim guidelines on diet and cancer|
a. Research at the international level. b. Research at the national level. c. Research at the local level. d. Research at the individual level.
NCI also is supporting a number of studies in China, where the unique distribution of nutrients in the soil provides a natural laboratory for studying disease. For example, areas of the terrain differ widely in selenium content, and evidence exists that selenium deficiency may be associated with increased cancer risk. Another prevention intervention study in China involves administering multiple vitamin/mineral preparations containing beta-carotene to oesophageal dysplasia patients. Although a rare tumour in the United States, 20 per cent of the deaths in Linxian, China, are due to oesophageal cancer. A prominent part of the population's diet consists of pickled foods, which are suspected to produce carcinogens over time. It has been suggested that the micronutrient deficiencies, in combination with the carcinogenic substances, lead to cancer. A second, related trial involves administering a series of micro-nutrients to a general Chinese population using a multi-factorial design.
Among the international laboratory studies being supported by NCI is a project that began by looking at the possible cancer-promoting effects of saccharin and tryptophan in human and rat bladder tissues. The London researchers now are comparing the effects of these cancer promoters to anti-promoters such as retinoids, and are gearing up for human prevention studies.
Finland provides a unique resource for studying the intervention of beta-carotene and vitamin E in a population of heavy smokers. Because of the country's past problems with tuberculosis, its public health service requires every male smoker to have an annual chest X-ray. This practice provides an opportunity to superimpose a low-cost nutritional intervention study into a system which already provides population surveillance, and good record-keeping. The five-year, double-blind randomized trial will also include a dietary survey of persons from the original cohort who subsequently developed cancer.
With respect to cancer treatment, researchers in Toronto, Canada, are studying perturbations of various nutritional parameters in breast and lung cancer patients, and are examining whether these deficiencies are correctable with existing methods of nutritional intervention. Investigators are applying expertise in nutritional assessment and in measurement of total body nitrogen with neutron activation.
United States studies
Within the United States, NCl's nutritional focus comprises two areas: (a) diet and cancer prevention, and (b) chemoprevention. Current and proposed projects that could benefit from the development of INFOODS include a large epidemiologic investigation, which is examining dietary patterns of the migrant Japanese in Hawaii and cancer incidence. Using epidemiologic data and sera samples collected from 1965 to 1968, incident cancer cases are being evaluated. The study also will examine the relationship between future cancer incidence and intakes of dietary fat, fibre, alcohol, dietary nitrates, salt, vegetables, and other food constituents.
A multi-institution clinical trial, now under way in eight US cities, is studying the effect of a low-fat diet (i.e. 20 per cent of total calories) on women at high risk for breast cancer. This protocol will test whether manipulation of dietary fat will slow or halt the subsequent promotion phase of cancer in women who have a predisposition for breast cancer.
The need for a comprehensive food data system such as that proposed by INFOODS is shown in studies on dietary fibre at Cornell University and the University of Wisconsin. Among the problems with existing fibre data are lack of standardized analysis techniques on representative foods, incomplete data, and lack of information about the meaning of current fibre values. Van Soest and Marlett are working to develop methods for fibre analysis and to analyse total fibre and individual dietary fibre components in US foods.
Similar dietary data problems exist for the food composition of carotenoids and retinoids. NCI supports several case-control studies that seek to demonstrate that levels of vitamin A consumption affect the development of colonic adenomatous polyps and adenocarcinoma. One three-year clinical trial using beta-carotene will attempt to slow the rate of polyp development and redevelopment. Vitamin A status will be assessed through blood plasma levels and dark adaptation tests. The advantage of using colonic adenomatous polyp formation, a pre-cancerous condition, as an endpoint in this trial is that the condition has a short development and redevelopment time in many patients.
In other related studies, vitamin A is being administered to persons with asbestosis, for treatment of lung mesothelioma, and to chronic and former smokers for prevention of lung cancer. Women at high risk for cervical dysplasia are taking retinyl acetate in two other trials.
A new area of NCI-sponsored research involves identifying, characterizing, and validating the dietary markers of past or present dietary exposure to cancer. Various problems exist in interpreting data derived from current nutritional assessment techniques. Moreover, the latency period of carcinogenesis poses several problems in gathering information about past dietary habits, namely that: (a) current dietary intakes may not be representative of past intakes, since dietary patterns change over time, and (b) our knowledge of the changing composition of foods is limited. Markers of both present and past dietary experience, therefore, will be especially useful in nutritionally focused studies in cancer epidemiology.
Clinical Nutrition Research Units (CNRUs) are an example of NCI-supported activities at the local level that would benefit from an integrated food data system. CNRUs are designed to create or strengthen nutrition research, training, and education through co-ordinated effort, intellectual stimulation, and use of shared resources. Each CNRU consists of: research with human subjects and populations; laboratory investigations; research training; educational programmes for medical students, house staff, practicing physicians, and paramedical personnel; nutritional support services; public information activities; and shared facilities and research services.
The NCI supports two CNRUs: one at the University of Alabama in Birmingham, and the other at the Memorial Sloan-Kettering Cancer Center, New York Hospital Cornell Medical Center, and Rockefeller University in New York. Primary areas of research at the University of Alabama concern malnutrition of hospital patients, nutrition and cancer feeding problems, vitamin status assessment, and folic acid biochemistry and metabolism. In one study, researchers found that the intakes of women with cervical dysplasia were often low in ascorbate and deficient in folate. Moreover, folate supplementation resulted in reversal of the dysplasia. Investigations at the Memorial SloanKettering CNRU focus on nutrition and its relationship to cancer, immunology, burns, pharmacology, and the brain as well as metabolism, diabetes, and lipids. To help find optimal ways to prevent and treat weight loss, cachexia, and other metabolism derangements that occur with cancer, CNRU researchers are examining whether riboflavin deficiency in experimental animals affects suppression of T-cells by syngeneic tumours.
At the individual level, NCI is involved with cancer information dissemination programmes, which aim to influence the general public's dietary patterns. The NCl's goal is to reduce cancer mortality by 50 per cent by the year 2000. As part of its Cancer Prevention Awareness Program, the Office of Cancer Communication (OCC) is developing a national campaign to emphasize dietary changes which reduce an individual's risk of cancer. The OCC has designed publications and public service announcements promoting increased consumption of dietary fibre and decreased consumption of fat.
Uses of food composition data
As evident form the above discussion, NCI-supported researchers at the international, national, local, and individual levels vary in the sophistication of food composition data they would require. Scientists involved in international projects need a system with familiar names of foods, standard units of measurement, and foreign-language translations of data to understand better the relationship between nutrient intakes and cancer incidence patterns throughout the world. If associations between certain nutrient deficients (e.g. selenium) and cancer are confirmed, INFOODS could assist international agencies in identifying foods that must be imported to satisfy nutritional requirements and help prevent cancer.
National NCI-supported studies have a need for more standardized analysis techniques to permit intra-study comparisons, particularly with regard to fibre, carotenoid, and retinoid composition. Researchers would benefit from the standardization of sampling and analysis procedures, modes of data expression and conversion factors, and other guidelines developed by INFOODS. INFOODS vocabulary that would be particuiarly important include origin, part, process, and stage of maturity.
At the local level, access to a food data system would not only assist CNRU laboratory and clinical investigations, it would be useful in nutrition research training, nutritional support services, and the nutrition education activities of professionals, patients, and the general public. For example, medical and surgical residents or other professionals pursuing advanced nutrition training could be instructed about the INFOODS system and its standards and guidelines relating to data gathering, storage, interchange, and usage. The information could then be utilized in their research, which would ultimately contribute to the expansion of the INFOODS network.
At the individual level, consumers must be aware of the dietary modifications they can make to reduce their risk of cancer, the second leading cause of US mortality. The valid and reliable data managed by INFOODS ultimately could be used to guide the daily food choices of the American public.
Implications for infoods
What are the implications of this NCI-supported research for the development of INFOODS? First, to meet the needs of NCI-supported researchers, an internationally acceptable identification and classification scheme must be developed. The goal should be a non-hierarchical vocabulary, which is flexible and allows the future addition of other factors such as treatment or processes, level of maturity, and grade or quality descriptions. Second, any system must permit the user to describe exactly the type of printout or analysis needed. The NCI-support research projects illustrate the diversity of users of food composition data and the unique requirements of each study. While some researchers need complete tables with specialized information, others are focusing on the analysis of a single nutrient.
Finally, it is recommended that an attempt be made to anticipate the features that sophisticated statistical techniques will require. Statistical interpretation of data is, of necessity, an important function of any data system for all researchers, regardless of whether their focus is cancer, cardiovascular disease, diabetes, or another disease.
In summary, NCI supports various research projects, at the international, national, local, and individual levels, which depend on food composition data. Although the five levels of users vary in the sophistication of the information they require, all need access to a system of food data which is relatively simple to use and contains reliable data. Any system developed also must be sufficiently flexible to permit expansion or other modifications to accommodate new trends and needs. The internal structure of the data system should accommodate various statistical analyses and printout formats for researchers' unique study requirements. Such a system would promote international participation and co-operation and, in all probability, significantly improve research.